The development of effective vaccines is of significant importance in the control and prophalaxis of diseases. The use of synthetic peptides as immunogens is being intensively investigated as one promising approach to the preparation of safe and effective subunit vaccines (Lerner, R. A., Green, N., Alexander, H., Liu, F.-T., Sutcliffe, J. G., and Shinnick, T. M. Proc. Natl. Acad. Sci. USA 78:3403-3407 (1981); Bhatnagar, P. K., Papas, E., Blum, H. E., Milich, D. R., Nitecki, D. Karels, M. J., and Vyas, G. N. Proc. Natl. Acad. Sci. USA 79:4400-4404 (1982); Neurath, A. R., Kent, S. B. H., and Strick, N. J. Gen. Virol. 65:1009-1014 (1984); Dreesman, G. R., Sparrow, J. T., Frenchick, P. J., and Kennedy, R. C. Adv. Exp. Med. Biol. 185:129-137 (1985); Thanavala, Y. M., Brown, S. E., Howard, C. R., Roitt, I. M., and Steward, M. W. J. Exp. Med. 164:227-236 (1986); Muller, G. M., Shapira, M., and Arnon, R. Proc. Natl. Acad. Sci. USA 79:569-573 (1982); Kennedy, R. C., Henkel, R. D., Pauletti, D., Allan, J. S., Lee, T. H., Essex, M. and Dreesman, G. R. Science 231:1556-1559 (1986); Bittle, J. L., Houghten, R. A., Alexander, H., Shinnick, T. M., Sutcliffe, J. G., Lerner, R. A., Rowlands, D. J. and Brown, F. Nature 298:30-33 (1982) and DiMarchi, R., Brooke, G., Gale, C., Cracknell, V. Doel, T. and Mowat, N. Science 232:639-641 (1986)). However, the development of synthetic peptide vaccines has been hampered by the need for both carriers and adjuvants which frequently have undesirable side effects (Lerner, R. A., Green, N., Alexander, H., Liu, F.-T., Sutcliffe, J. G., and Shinnick, T. M. Proc. Natl. Acad. Sci. USA 78:3403-3407 (1981); Bhatnagar, P. K., Papas, E., Blum, H. E., Milich, D. R., Nitecki, D. Karels, M. J., and Vyas, G. N. Proc. Natl. Acad. Sci. USA 79:4400-4404 (1982); Neurath, A. R., Kent, S. B. H., and Strick, H. J. Gen. Virol. 65:1009-1014 (1984); and Muller, G. M., Shapira, M., and Arnon, R. Proc. Natl. Acad. Sci. USA 79:569-573 (1982)). In addition, immunization with peptide-protein carrier complexes usually results in the priming of the T cells to the foreign carrier. Hence, a natural infection does not produce a secondary immune response since the animal's T cells are not primed to the natural carrier of the neutralizing epitope.
Accordingly, there still exists a need for effective immunogens which do not require that the peptides be linked to heterologous protein carriers and do not require injection in conjunction with additional adjuvants.